One example of a conventional disk driving apparatus will be explained with reference to FIGS. 14 and 15.
A disk driving apparatus 1 comprises a body chassis 2 and a tray 3 which can slide with respect to the body chassis 2. The tray 3 comprises a tray base 4 made of synthetic resin, and a thread chassis 5 fitted and fixed to the tray base 4. The thread chassis 5 comprises a thread base 6 into which a spindle motor 50 and a head driving mechanism are incorporated, and a metal cover for covering both upper and lower surfaces of the thread base 6. In FIG. 14, a reference numeral 8 represents a head, and a reference numeral 9 represents a rotary table 9. An auxiliary circuit substrate 12 for controlling the spindle motor 50 and the head driving mechanism is disposed in the tray 3.
A main circuit substrate 11 is disposed in the body chassis 2. A connector 13 of the main circuit substrate 11 and a connector 14 of the auxiliary circuit substrate 12 are interconnected through an FPC (flexible printed circuit) 51. The FPC 51 is formed into a U-shape as a whole in which a conductive path is formed on a polyester film by printing technique.
A first end of the FPC 51 is connected to the connector 13 of the main circuit substrate 11. A straight line portion connected to the first end (portion 51a closer to the body chassis) is fixed on to the body chassis 2. A straight line portion (portion 51b closer to the tray) connected to a second end of the FPC 51 is once brought upward and then is folded back substantially at an angle of 180° toward the tray 3 as shown in FIG. 14. The folded back second end 51b of the FPC 51 is connected to the connector 14 of the auxiliary circuit substrate 12. A part of the FPC 51 which is folded back at the portion 51b closer to the tray toward the tray 3 is formed with a folded-back curved portion 19 having a U-shaped cross section.
When the tray 3 is pulled out from the body chassis 2 or pushed into the body chassis 2, the tray 3 moves and the portion 51b of the FPC 51 closer to the tray also moves together, and the folded-back curved portion 19 also moves in the same direction at a half speed of the moving speed of the tray 3. In this manner, even when the tray 3 moves toward or away from the body chassis 2, the connected state between the connector 13 of the main circuit substrate 11 and the connector 14 of the auxiliary circuit substrate 12 is always maintained through the FPC 51.
When rigidity (spring force) of a base member of the FPC 51 is excessively high, however, a radius of curvature of the folded-back curved portion 19 becomes great and a part of the folded-back curved portion 19 rises high and this portion abuts an upper lid 2a of the body chassis 2 and pushes the same. When the tray 3 is pulled out from the body chassis 2 or pushed into the body chassis 2 in this state, the folded-back curved portion 19 comes into contact with the upper lid 2a and it becomes difficult for the folded-back curved portion 19 to move due to friction and thus, the radius of curvature of the folded-back curved portion 19 tries to further increase. As a result, there is an adverse possibility that it becomes difficult to move the folded-back curved portion 19 or a part of the FPC 51 rub against the upper lid 2a of the body chassis 2 by this movement and is damaged.
To solve this problem, Japanese Patent Application Laid-open No. 10-199207 discloses a technique in which a guide sheet made of polyethylene terephthalate which moves together with the tray is interposed between the body chassis and the FPC, thereby preventing the folded-back curved portion of the FPC from coming into contact directly with and rubbing against the upper lid of the body chassis.
However, since the polyethylene terephthalate which is a material of the guide sheet used for preventing the friction between the body chassis and the FPC has low bending rigidity, the guide sheet itself is bent by the friction with the body chassis, and there is a problem that smooth sliding motion of the tray is impaired.
To solve such a problem, when the bending rigidity of the FPC 51 is lowered by reducing a thickness of the base member of the FPC 51 or using softer material, the radius of curvature of the folded-back curved portion 19 becomes relatively small and a case in which a part of the FPC 51 strongly pushes the upper lid 2a of the body chassis 2 can be avoided. When the tray 3 is at an unload position, however, a part of the portion 51b of the FPC 51 closer to the tray lops from a gap W formed between (the lower cover 7b of) the thread chassis 5 and the body chassis 2, as shown in FIG. 5 and protrudes from the thread chassis 5.
When the tray 3 is pushed into the body chassis in a state in which the FPC 51 lops from the gap W between the thread chassis 5 and the body chassis 2, there is an adverse possibility that the lopping FPC 51 is sandwiched between the body chassis 2 and the thread chassis 5.